(1) Field of the Invention
The present invention generally relates to digital-to-analog converters, and more particularly to a digital-to-analog converter having variable circuit parameters which determine the voltage range of an analog output signal.
(2) Description of the Prior Art
Digital-to-analog converters (hereafter simply referred to as D/A converters) are widely used in various electronic devices. Conventional D/A converters have fixed circuit parameters which determine the state of the analog output voltages (voltage range), and are thus suitable for very limited or specific applications. For example, the D/A converter converts a digital signal into an analog signal swinging within a voltage range defined by a high-potential-side reference voltage and a low-potential-side reference voltage. Recently, a chip having a plurality of D/A converters has been manufactured. Normally, the high-potential-side and low-potential-side reference voltages are applied in common to the on-chip D/A converters. Thus, the D/A converters have identical analog output voltage ranges. If the high-potential-side and low-potential-side reference voltages are externally varied, the identical analog output voltage ranges of the D/A converters will be changed. However, it is impossible for the on-chip D/A converters to have the different output voltage ranges. It may be possible to provide external terminals for the respective on-chip D/A converters and supply different reference voltages thereto. However, such a possible arrangement would have a larger number of terminals.
As described above, conventionally, it is very difficult or impossible to provide various D/A conversion characteristics of the single D/A converter and provide the mutually different D/A conversion characteristics of the on-chip D/A converters.